PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Actual Returns on Assets Held by Our Pension Trusts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Actual return on plan assets	$ 27	$ 226	$ 368
Direct investments
Defined Benefit Plan Disclosure [Line Items]
Actual return on plan assets	12	175	258
Derivative instruments
Defined Benefit Plan Disclosure [Line Items]
Actual return on plan assets	$ 15	$ 51	$ 110